Theoretical and practical assessment of busring temperatures at the Dinorwig power station

The Dinorwig pumped-storage power station has six generator-motors which are vertical 3 phase, 12 pole machines rotating at 500 RPM and are rated at 330 MVA 18 kV. High temperatures in excess of the BS2757:1986 Class B limits of 130°C, have been encountered at various points along these busrings for certain machine load conditions, giving cause for concern about insulation life and the integrity of brazed joints. In order to investigate the nature and extent of the problem several finite element studies were carried out. The results were then used in a thermal network to provide predictions of busring copper temperatures. Several proposals were put forward to try to reduce these high temperatures including altering the conductor size of the busring and using a new high thermal conductivity insulation. The most economical solution was implemented and temperature measurements were taken during machine operation to confirm it´s effectiveness